The story is very interesting. Oil was pumped during the long trip to make-up for oil loss/consumption. One aircraft apparently had zero oil loss/consumption, so the excess oil eventually foiled the plugs, leaving the hugely overweight aircraft with only the lower-efficiency front engine, which was unable to stay aloft.
For the whole story, go to my Skymaster website at
www.SkymasterUS.com and click on the link "History of the Skymaster". The incident is described at the bottom of page 7 and top of page 8.
Ernie